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Color of clothes - heat management

  1. May 19, 2007 #1

    JPC

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    hey just wondering

    is it because you wear a white shirt that you're going to feel less heat, and because you wear a black shirt that you're going to feel more heat like everyone thinks ?

    does it depends on the material ?
    on the heat conductance of the material ?

    because from what i think :

    if material heat conductance = high then
    if material color = white then
    less light is absorbed : more pass through shirt to skin
    end if
    if material color = black then
    more light is absorbed > shirt gets hot > because of shirt-skin contact skin gets hot
    end if
    end if

    if material heat conductance = low then
    if material color = white then
    less light is absorbed : more pass through shirt to skin
    end if
    if material color = black then
    more light is absorbed > shirt gets hot > but because of low heat conductance skin doesnt get hot
    end if
    end if

    from my reasoning , it would be better a black low heat conductant shirt

    Am i right ?
     
  2. jcsd
  3. May 19, 2007 #2

    Astronuc

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    Staff: Mentor

    White shirts are white because they reflect more of the visible light spectrum. Shirts have a particular color because the material, or rather die, reflects that particular color (wavelength) while absorbing others.

    less light is absorbed - therefore there is less heat to be conducted to the skin.

    Shirts also need to 'breath' - exchange air, so in addition to absorbing light, transfer of air (advection/convection) from the skin (and water vapor from perspiration/sweat) aids in removing heat.

    No. Remember that the body produces heat, so shirt of low thermal conductance (more thermal resistance) would likely make one warmer.

    A black shirt with low thermal conductivity would be ideal on a cold day where the objective is to absorb heat.
     
  4. May 19, 2007 #3

    JPC

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    so whats best during hot days
    is a high heat conductor white shirt ?
     
  5. May 19, 2007 #4

    Danger

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    Gold Member

    The conduction of heat depends upon the physical characteristics of the material, not the colour. The colour is resonsible for the absorbtion of light, including IR, that produces heat.
    It's not coincidental that most tennis players and golfers wear white.
     
  6. May 19, 2007 #5

    JPC

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    i know, thats why i made a clear distinction between the conduction of heat and color
     
  7. May 19, 2007 #6

    Danger

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    I suspect a bit of a language barrier is at work here. My apologies for misunderstanding your previous post; I thought that you were equating white with high conductivity.
     
  8. May 19, 2007 #7

    JPC

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    is it this type of language that confused you ?

    its just my way of organising possibilities,
    its a bit the programming way, but for me it looks clear

    ' reminder for those who didnt read the begining of the post : what i have quoted from myself is wrong
     
  9. May 19, 2007 #8

    Danger

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    Gold Member

    Actually, it was post #3 that I was referring to.
    In the one that you referenced, though, I see a problem that might be the root of it all.
    Line 3--Less light is absorbed, more pass through shirt to skin.
    That is incorrect. Less light is absorbed because it is reflected away from the material. The higher the absorbition, the greater the conductive transfer to the person within.
     
  10. May 19, 2007 #9

    Astronuc

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    Staff: Mentor

    A white shirt that maximizes flow (mass transport) of air (advection/convection).
     
  11. May 19, 2007 #10

    DaveC426913

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    Gold Member

    ... and passes moisture.

    That's why white natural fibres (such as cotton) are the best.
     
  12. May 27, 2007 #11
    Does that mean that a black guy would be hotter thank a albino-white guy in the same temperature?

    Also, how does one matter "absorb" heat?
     
  13. May 27, 2007 #12

    Danger

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    I'm not a genetictist, but I do have a lot of black family. A black person absorbs more heat, but the reason s/he is black is because the line evolved to deal with a lot of direct sunlight. The excess melanonin is there to protect them from UV.
    This is actually getting more into Moonbear's and Adrenaline's field (and maybe Doc Toxin if he's still around). I really don't know too much about it.
     
  14. May 27, 2007 #13
    Yes, that is basically the point. Dark skin stops the UV rays from penetrating the skin and causing cancer.
     
  15. May 29, 2007 #14
    But how does one matter "absorb" heat? And Why do the two things relate?
    Is there a link that would explain this to me?
     
  16. May 29, 2007 #15
    For two clothes of roughly the same materials (say, a cotton tee-shirt), they have almost identical heat conduction. This is when heat is transferred through contact, such as a pan on a stove; in this case, it would be the hot air and the shirt coming in contact.

    However, a white color will reflect most UV rays from the sun (most of the energy from sunlight is not visible light), whereas a black shirt will absorb the UV rays, adding this energy to the shirt in the form of heat.

    This is analogous to the way microwaves heat up water very quickly, while not heating glass hardly at all.
     
  17. May 29, 2007 #16
    the person with darker would feel the heat more fromt he sun because his body makes more melanin but at the end of the day he would be fine a bit hotter but fine, while the albino, while staying just a slight bit cooler at skin level, now has extreme sunburn all thorughout his body and is diagnosed with skin cancer a few weeks later.

    his lighter skin can keep him a bit cooler but it does nothing to prevent the harmful radiation from getting past his outer dead skin cells and into his living cells where he may get cancer. a darker person absorbs more of it with the outer cells that are both dark and dead, which reduces the chances of them getting any further where they might do damage.
     
    Last edited: May 29, 2007
  18. May 30, 2007 #17

    Danger

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    Gold Member

    While I agree with everything that you said, King, I think that the absorbtion or reflection of IR is more significant that that of UV as far as the heat thing goes. UV is more of a health issue, for sure, but IR is the primary medium of heat transfer.
     
  19. Jun 9, 2007 #18

    JPC

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    hey but how come the IR heat up materials more than UV ?
    and why people say IR go longer distances

    the way i see it :

    UV have faster frequencies, they should have more energy
    while IR have slower frequencies, should have less energy

    or is it that when hitting a electron , photons that vibrate faster transfer less energy to the electron ?

    ---

    and as for the distance , i thought photons would carry on forever
    so is it that high frenquence photons loose their energy faster ?

    ---
    and do photons see their frequencies slower as they get in contact with matter ?
     
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